There has been an increase in interest in processes for the manufacture of small devices in the field of biological and biochemical analysis. The manufacture of devices used for analytical testing uses techniques similar to those used in the electronics industry. Examples of these manufacturing techniques include photolithography and wet chemical etching. The devices are often made from solid substrates such as silicon and glass.
Microanalytical devices have been used for performing various analytical reactions. For example, U.S. Pat. No. 5,498,392 to Wilding et al. discloses a mesoscale device having microfabricated fluid channels and chambers in a solid substrate for the performance of nucleic acid amplification reactions. U.S. Pat. No. 5,304,487 to Wilding et al. discloses a mesoscale device having a cell handling region for detecting an analyte in a sample. The microchannels and chambers have a cross-sectional dimension ranging from 0.1 micron to 500 microns. U.S. Pat. No. 5,885,470 to Parce et al. discloses a microfluidic transport device made from a polymeric substrate having fluid channels that can be a few microns wide.
The prior processes for microfabrication of polymeric substrates typically involve stamp molding or embossing. These processes often require the use of a release agent or coating on the molding surface.
There has also been an increased interest in microneedle injection for the transdermal delivery of various drugs. The microneedle devices can have a plurality of microneedles with a length of a few hundred microns. These devices are usually made from silicon or other metals using etching methods. Although effective, the resulting microneedle devices are expensive to manufacture and are difficult to produce in large numbers. One example of a microneedle device for delivering a drug to a patient is disclosed in U.S. Pat. No. 5,879,326 to Godshall et al.
Microneedle drug delivery devices are able to penetrate the stratum corneum of the skin with less irritation. The stratum corneum is a complex structure of compacted keratinized cell remnants having a thickness of about 10–30 microns and forms a waterproof membrane to protect the body from invasion by various substances and the outward migration of various compounds. The delivery of drugs through the skin is enhanced by either increasing the permeability of the skin or increasing the force or energy used to direct the drugs through the skin.
One method of delivering drugs through the skin is by forming micropores or cuts through the stratum corneum. By penetrating the stratum corneum and delivering the drug to the skin in or below the stratum corneum, many drugs can be effectively administered. The devices for penetrating the stratum corneum generally include a plurality of micron size needles or blades having a length to penetrate the stratum corneum without passing completely through the epidermis. Examples of these devices are disclosed in U.S. Pat. No. 5,879,326 to Godshall et al.; U.S. Pat. No. 5,250,023 to Lee et al.; and WO 97/48440.
The prior methods and apparatus for the manufacture of micro-devices for medical use has exhibited some success but is generally time consuming and expensive. Accordingly, a continuing need exists in the industry for an improved method for the manufacture of micro-devices.